Many drinking bottles have a single chamber for holding a beverage fluid. As a result, during consumption of a beverage by a user, backwash can easily flow into the bottle and contaminate the remaining fluid with biological agents. Such backflow potentially contains microbes, enzymes, and other biologically active agents, which can contaminate a beverage and reduce its drinkability. For example, bacteria can grow in beverages, particularly beverages that contain sugar and other nutrients. Consequently, if the remaining beverage is not consumed relatively quickly, it can spoil or become unsafe to drink.